1. Field of the Invention
The present invention generally relates to the field of substrate processing and, more particularly, to apparatuses and methods for preventing relative rotation of a vertical support shaft and a support structure for a wafer holder.
2. Description of the Related Art
In the processing of substrates, such as semiconductor wafers, a substrate or wafer holder is generally employed inside a reaction chamber to both evenly support a wafer and to ensure even heat distribution across the surface of the wafer. If the wafer holder helps to attract radiant energy, it is called a susceptor. The susceptor or wafer holder is supported by an underlying support (e.g., a quartz “spider”) having a socket which is configured to mate with a portion of an elongated rotation shaft. In one common configuration, the shaft is rotationally linked to a motor, which effectuates the rotation of the support. In turn, the wafer holder supported by the rotating wafer holder support is also rotated, as is the wafer resting upon the wafer holder. During wafer processing (e.g., chemical vapor deposition, physical vapor deposition, etching, etc.) it is desirable for the wafer to be evenly rotated. Even small deviations in the speed of rotation or “wobble” can result in uneven processing of the wafer surface, which is generally undesirable.
In the past, wafer holders have been designed for 200 mm wafers. Currently, larger, heavier wafer holders configured to accommodate 300 mm wafers are used more frequently due to their higher semiconductor device yield (e.g., microchip) made possible by the larger surface area of 300 mm wafers.